I have a Tektronix 577 curve tracer and I am recapping the power supply board that is located at the rear of the instrument. I am looking at replacing C744 which is a 250V 1700uF capacitor. I found a 250V 1800uF capacitor but the capacitor installed is a 275V capacitor though the manual states 250V. I am curious how much voltage typically runs across C744 so I don't destroy a capacitor, thanks

You should be fine. 20% above 200 volts would be 240 volts. BTW, the schematic shows the value C744 as 170 micro farad.

George KD6NEW

George and DW

Definitely a 170uF Cap. I would check the ESR on that old cap very carefully, if it checks "good" for capacity, ESR and ripple, leave it alone. I just finished with a 577 and the filter caps all checked good for ESR and Ripple current. In my experience, the 577 was much more plagued with bad tantalum caps. I found 7 bad ones on mine, which completely disabled the thing. Just my opinion and experience, of course. Best of luck in your project.

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Michael Lynch
Dardanelle, AR

Thanks for informing me C744 is a 170uF capacitor, I believe what happened I accidentally interpreted the u in uF as another zero and thought it was 1700uF, certainly made it easier finding a replacement capacitor. I am also replacing the insulator pads for U722 U732 Q788 Q766

https://www.digikey.com/products/en?keywords=TG6050-30-30-2%E2%80%8E%20 - I think this thermal pad should work, bought it in a sheet so I can cut the pieces I want to fit.